Air passenger stairs and air passenger bridges serving as access assemblies are well known from the prior art. Whereas air passenger stairs are driven up to the aircraft on the airfield and the passengers can thus board or leave the aircraft via the airfield, air passenger bridges are characterized in that a direct link is formed by air passenger bridges between the terminal building on the one hand and the aircraft on the other hand. With air passenger bridges or other access or loading assemblies, the docking operation takes place as follows: The air passenger bridge has a positioning drive with a control system. The positioning drive takes care of the displacement of the air passenger bridge on the airfield and an adjustment of the height of the air passenger bridge relative to the airfield. When the aircraft has reached its parking position and the air passenger bridge must be driven up to the fuselage of the aircraft in the area of the doorway, this is commonly carried out manually by operating personnel present in the air passenger bridge, wherein driving the air passenger bridge up to the aircraft fuselage is carried out e.g. manually by means of a joystick, which is connected to the positioning drive by way of the control system. The air passenger bridge has a sensor, which continuously measures the distance between the air passenger bridge and the aircraft. If the value of the distance between the air passenger bridge and the aircraft falls below a predetermined distance value during the approach, the speed at which the air passenger bridge approaches the aircraft is reduced. The distance at which the air passenger bridge reduces its speed when approaching the fuselage of the aircraft commonly amounts to approximately 2 m. The air passenger bridge itself has a canopy roof with a circumferential bumper, wherein at least one limit switch is disposed on its front side in the area of the floor. When the bumper comes to rest on the aircraft fuselage, the limit switch is activated, so that the control system of the positioning drive receives a control signal from the limit switch, which stops the positioning drive.
During the approach to the aircraft, an adjustment of the height of the air passenger bridge relative to the doorway of the aircraft is carried out at the same time. To this end, the air passenger bridge has another sensor, which determines the distance between the air passenger bridge and the airfield. This sensor is also connected to the control system of the positioning drive of the air passenger bridge, so that the air passenger bridge is lifted or lowered to a predetermined height upon receiving corresponding sensor signals.
Alternately, it can be provided that the current distance from the airfield determined by the sensor is displayed to the operating personal, and that the operating personal can accordingly adjust the height of the air passenger bridge manually.
If the air passenger bridge with the canopy roof and the frontal bumper rest on the aircraft fuselage in the area of the doorway of the aircraft, it is necessary to continuously determine the vertical relative movement between the aircraft fuselage and the air passenger bridge, which occurs while loading and unloading the aircraft. According to the prior art, a so-called auto-leveller is used to this end. The auto-leveller comprises a lever disposed at the air passenger bridge, which has a pressure roller or cylinder at its end, which rests against the aircraft skin in the area of the doorway. The pressure roller accommodates switches, which, depending on the number of rotations of the roller, transmit signals to the control system of the positioning drive of the air passenger bridge, said signals causing the air passenger bridge to be lowered or lifted relative to the aircraft, in order to compensate for differences in height caused by the relative movement.
A disadvantage of using an auto-leveller is that it is not always guaranteed that the roller will actually roll along the aircraft fuselage if the aircraft suddenly sags. Rather, there is a risk that the roller may carry out a slipping or sliding movement along the aircraft fuselage. A slipping movement can also take place in case of ice on the fuselage of the aircraft. Another disadvantage is that the docking cylinder or roller damages the aircraft skin during docking. This risk is particularly real in the case of carbon fuselages. The consequences of a sliding or slipping movement is that none of the switches in the roller or cylinder is actuated, and that the control systems of the positioning drive of the air passenger bridge thus does not receive a corresponding signal for lowering or lifting the aircraft passenger bridge. It creates a risk that the open door of the aircraft, which has been swung outward, will touch the floor of the air passenger bridge, thus causing damage to the aircraft and to the air passenger bridge. In order to avoid this, it is known to provide a so-called safety shoe, in addition to the auto-leveller, which is disposed between the floor of the air passenger bridge and the bottom edge of the door of the aircraft. If this safety shoe receives pressure from the aircraft door, the shoe also causes the air passenger bridge to be lowered, by providing a corresponding signal to the control system of the positioning drive. One disadvantage of the shoe is that it is freely accessible to boarding or exiting passengers. It has happened before that passengers would step onto the safety shoe, thus simulating a load that does not actually exist, so that the air passenger stair would be lowered with a jerk by several centimeters, causing boarding or exiting passengers to fall. In addition, the Pitot tubes of the aircraft located under the floor of the air passenger bridge can be torn off as a result of this uncontrolled movement. In addition, current systems are sensitive to humidity, which causes switching errors in the safety shoe.
From WO 01/34467 A1, it is known to use a sensor with a light source that emits electromagnetic radiation in a radiating direction and with a detector that detects electromagnetic radiation reflected by a surface of the aircraft for positioning a movable air passenger bridge against a door of an aircraft. In this regard, a transit time of the electromagnetic radiation from the light source to the detector is determined, based on which the distance, in the radiating direction, between the sensor and the aircraft is determined. In order to detect different points on a surface of the aircraft using the electromagnetic radiation and thereby to be able to determine a line profile of the surface, a pivotable mirror is provided, by means of which the radiating direction of the electromagnetic radiation can be varied. The line profile determined in this manner is used together with information concerning the position of the door on the aircraft stored in a computer, in order to correctly position the air passenger bridge against the aircraft in the area of the door.
The document U.S. Pat. No. 7,120,959 B2 discloses a method for positioning a mobile air passenger bridge against an aircraft, in which a difference in height between a sensor disposed at the air passenger bridge and an upper edge of the aircraft is determined by a sensor. Once the distance between a doorway and the upper edge is known, the height of the air passenger bridge can be adjusted to the height of the doorway as a function of the determined height difference and the known distance between the doorway and the upper edge. Concretely, U.S. Pat. No. 7,120,959 B2 proposes using a sensor having a light source that emits electromagnetic radiation, wherein the radiation angle of the electromagnetic radiation can be varied. In addition, the sensor comprises a detector, which detects electromagnetic radiation reflected by the surface of an aircraft. In case of a variation of the radiation angle, the radiation angle at which the electromagnetic radiation propagates over the upper edge of the aircraft can be determined based on the intensity curve of the reflected electromagnetic radiation detected by the detector, from which the height difference between the sensor and the upper edge of the aircraft can be inferred.
From the document DE 10 2011 101 418 A1, a mobile access or loading assembly for an aircraft and a method for positioning such an assembly on the fuselage of an aircraft is known, in which a single scanner is provided with which a position of the access or loading assembly relative to the fuselage of the aircraft is determined at certain time intervals. The position determined by the scanner is used to control a positioning drive, in order to orient the access or loading assembly relative to the fuselage of the aircraft. In order to orient it while approaching the aircraft, the distance between the access or loading assembly and the fuselage of the aircraft is determined by the scanner, wherein e.g. the speed of the approach can be controlled as a function of the distance. On the other hand, its height relative to the airfield is determined by the scanner, wherein the access or loading assembly is lifted or lowered to a predetermined value depending on the determined height. When the access or loading assembly rests on the fuselage, a line profile of the fuselage is determined by sensing a plurality of points on the fuselage. The determined profile is compared with a previously determined line profile of the fuselage in a computer unit connected to the scanner. If there is deviation indicating that a vertical relative movement of the access or loading assembly relative to the fuselage has occurred, the computer unit generates a signal for lifting or lowering the access or loading assembly, in order to compensate for the height difference associated with the relative movement. A single scanner does not allow a precise enough determination of the position of the aircraft fuselage, so that the e.g. access assembly cannot be positioned reliably. Since the scanner is attached to the end of the access assembly facing the fuselage, a very large angle is required for capturing the entire aircraft fuselage. Determining the contour of the aircraft fuselage requires many measurements with little modification of the rotation angle of the scanner. Due to the large scanning range (180°) and the low angular resolution, a great number of measurements are required. As a result the measuring time is considerably lengthened, which does not allow for rapid adjustments of the position of the access assembly in case of sudden position changes of the aircraft fuselage.